I started with gen 2
7 > 2 > 5 > 4 > 3 > 6 > 1
don't hate kanto or anything, just firmly believe gen one is the most unplayable due to its mechanics, glitches and awful graphics.
I have fond memories of gen 3 but it's intensely overrated, didn't add nearly as much as gen 2 added/fixed, and the fact that they didn't add physical/special split was inexcusable, especially considering they knew water and dark were special, then proceeded to make crawdaunt and sharpedo.
gen 2 added breeding, genders, night and day cycles, happiness, a female protagonist, shinies, dark and steel type, berries, held items, and looked so much better than gen 1 (and did so without an immense amount of glitches)
gen 4 added physical special split, and HGSS was great, music was nice too, and the dex was pretty solid
gen 5 was solid, and they actually catered to some of the interests of competitive players
gen 6 was eh but megas are cool
7 is looking to be fantastic but it's obviously too early to tell right now